Four in five households are living in "transport poverty", according to figures highlighted by the RAC Foundation.
These households spend more than 10% of their disposable income on public and private transport, with most of the money going on buying and running a car, said the foundation.
The lowest-earning households spend 9% of their disposable income on transport, while the highest-earning fork out 15.5%. On average, households - both car and non-car owning - spend 14% of weekly expenditure on transport, with £64.90 being spent out of a total of £473.60.
RAC Foundation director Professor Stephen Glaister said: "Rightly, there is much concern about the four million households who need to spend more than 10% of their income to keep warm.
"Yet this figure is dwarfed by the 21 million households which spend over 10% on transport. For the average household, transport is the single biggest outgoing, bar none."
He went on: "The situation is even starker when you look only at those homes which have a car or van. In these cases, the poorest fifth of households are spending at least 17% of income on a vehicle - leaving aside anything extra that goes on public transport.
"Just like heating our homes, most of us have to spend money on transport. There is no choice.
"While savings can be made at the margins by making fewer journeys and combining those which are essential, people have no option other than to go to work, visit the supermarket, see the doctor and take the children to school. That means paying for transport."
Prof Glaister continued: "The public finances are a matter for the Chancellor, but when he makes decisions about the rate of fuel duty he must be aware of their impact on the 34 million people who drive.
"It is true the cost of buying a car has fallen over recent years, but the cost of running one has soared. While most people can delay replacing their vehicle, they have little or no choice about filling it with fuel, getting it taxed and insured, and keeping it maintained."